Coupling speed control device



March 1960 A. M. CRAWFORD ET AL 2,930,388

COUPLING SPEED CONTROL DEVICE 2 Sheets-Sheet 1 Filed March 5, 1956 INVENTORS. Arc/7111a M M flra Wfiam, Kenna HIM Lacherby &

fi'obzryifigiw, BY I A TTORNEYS.

March 29, 1960 A. M. CRAWFORD ET AL 2,930,888

COUPLING SPEED CONTROL DEVICE Filed March 5, 1956 2 Sheets-Sheet 2 FIG: 8

INVEN TORS Archiba/dfl 67a Wfard,

A TTORNEYS.

United States Patent F COUPLING SPEED CONTROL DEVICE Archibald M. Crawford, Pittsburgh, Pa., Kenneth M.

Lockerby, Towson, Md., and Robert H. Brown, Pittsburgh, Pa.

Application March 5, 1956, Serial No. 569,648

7 Claims. (Cl. 246-124) This invention relates to coupling speed control devices and more particularly concerns apparatus and method for detecting and indicating the presence of a railroad car on a section of railroad track. This invention'further relates to an apparatus and a method for detecting and indicating the passage of a train over a particular short length of track.

In routing and delivering railroad freight cars, a freight train made up, for example at Chicago, includes cars having various destinations along the. east coast. This train, and similar trains, will proceed to a central point called a classification yard. The classification yard has a number of receiving tracks for receiving the incoming trains, a hump, and a number of classification tracks for making up the outgoing trains. A control tower is provided and retarder devices are placed on the tracks intermediate the hump and the classification tracks.

In making up the outgoing trains, the procedure is to uncouple the cars of the incoming trains and move them to the hump. As an example, a car destined for Philadelphia is moved to the hump which is at a higher elevation than the classification tracks. The car is moved off the hump down an incline which, through the force of gravity, imparts a certain speed to the car. Appropriate switches are operated from the control tower to connect the track leading from the hump to the classification track where the Philadelphia train is being made up. If this car is to be the first car of the train it is desirable that it proceed at such speed that it will come to a gentle stop at or near the far end of the classification track; and if this car is to be the last or an intermediate car of the train, it is desirable that it come to a gentle stop just short of the preceding car. If a car were to proceed at the speed of the first car into the classification track, or even at a greater speed, the following car would crash into the preceding car and the impact would possibly damage both the car and its merchandise. Therefore, retarder devices are provided which slow down following cars to an appropriate speed, and these retarder devices are controlled from the control tower. However, in order to select the proper speed for a car, the tower operator must know how many cars are already on a particular classification track and must know their position on that track. In clear weather, this presents little problem since the operator can see the cars on the classification track, but in hazy or stormy weather and at night, this is not possible. Under such conditions, there has long been a need for apparatus that signals to the operator the presence or absence of a railroad car on a section of track.

Although it has heretofore been suggested to provide apparatus for indicating the presence of a car on a particular section of track, some of the devices heretofore known have, through failure of the apparatus, incorrectly indicated that the track was unoccupied and as a result, rolling stock and its contents have been damaged due to the false signal. Other prior art devices have mechanically counted the cars as they passed a point at.

the beginning of the classification track; but if the car stopped short before reaching its destination due to the vagaries of wind, rain, ice and car lubrication, the following car would crash into it, causing damage to the car and its goods. Others of the previous devices required that the rails have insulated joints, and some devices required a separate circuit, including separate batteries and other components which are expensive, for each section of each classification track. Still other prior art devices requiredthat considerable length of insulated wire be mounted in proximity to the track in the form of a loop.

Accordingly, it is an object of this invention to provide apparatus for overcoming the aforementioned difficulties. It is a more specific object to provide apparatus that is adapted for trafiic control and coupling speed .control of railroad cars assigned to a classification track. It

is another object to provide apparatus of this type that is relatively inexpensive, that has relatively few moving parts, and that is extremely easy to maintain.

Another object is to provide apparatus of this character that will indicate the presence of a car on a section of track, and in case of failure of the apparatus, includes a safety means which indicates that a car is present.

Still another object of the invention is to provide anapparatus of the character heretofore indicated which, includes a plurality of receiver means which have a com-- mon source of electrical energy.

Another important application of the apparatus of this,

Further objects and advantages of the invention, in-' cluding the economy and simplicity of the same and the ease with which it may be applied to existing railroad classification systems, will further become apparent in the detailed description to follow, throughout which reference is made to the accompanying drawings wherein:

- Fig. 1 represents a diagrammatic view of one specific. form of apparatus constructed in accordance with this.

invention; and

Fig. 2 represents a diagrammatic view showing a modified form of the invention.

Although specific terms are used in the following description for clarity, these terms are intended to refer only to the structures shown in the drawings, and are not intended to define or limit the scope of the invention.

Turning now to the specific embodiments of the invention selected for illustration in the drawings, the number 11 designates generally a classification track with its two rails 12 and 13, which is divided, into four sections a, b, c, and d indicated by the dotted lines 14, 15, 16, 17 and 18. Receiver units A, B, C and D are shown in Fig. 1,

unit A being associated with track section a, unit with section b, C with c, and D with d. An oscillator 21 is provided, which is preferably an type sine wave oscillator that has poor voltage regulation as one of its characteristics. If an oscillator having good voltage regulation is used, a resistor is incorporated in the oscillator circuit to give the circuit the poor voltage regulation required for the practice of this invention. Connected across the oscillator 21 is an amplifier 22 that is connected by conductors 23, 24 across rails 12 and 13 and also across the primary windings 25 of transformers The secondary windings 27 of the transformers are connected into a receiver circuit including an indirectly' Patented Mar. 29, 1960" heated gas tetrode 28 having an anode 31, a cathode 32, a control grid 33, a screen grid 34 and a filament 35. Filament 35 is heated by any electrical source. Screen grid 34 is tied to cathode 32 at a terminal 64 and therefore assumes the potential of cathode 32.

' Tube 28 is provided with a control grid circuit which receives energy from the track circuit. The track circuit includes rails 12, 13, oscillator 21, amplifier 22, conductors 23, 24, and the primary winding 25. Oscillator 21 applies electrical energy to both the track circuit, and (through transformer 26) to the control grid 33 of tube 28. The control grid circuit includes secondary winding 27, a rectifier 36, a capacitor 37 and a resistor 38 connected across winding 27 and rectifier 36. Also included in the control grid circuit is a resistor 41a and 'a variable bias resistor 42a having a capacitor 43 connected across it. Like numbers are used to designate like parts in the receiver units A, B, C and D, except that the bias resistors are designated 42a, 42b, 42c and 42d, respectively, and the control grid resistors are designated 41a, 41b, 41c and 41d, respectively. The voltage applied to the rails from oscillator 21 through amplifier 22, therefore, causes a voltage to be applied to the control grid 33 of tube 28, this track voltage being rectified and opposed by the negative bias. voltage supplied by bias resistor 42a and the negative bias circuit.

Bias resistor 42a is included in a biasing circuit that can be traced from terminal 44 of transmission line 45 through terminal 46, wire 47 having a rectifier 48, preferably a selenium rectifier, and a resistor 51 connected in series with the parallelled' resistor 42a and capacitor 43, through wire 52 and terminal 53 back to transmission line 45 at terminal 54.

. An anode-cathode or plate circuit for tube 28 includes anode 31, a resistor 55, a relay 56 having a capacitor 57 connected across it, the secondary winding 58 of a transformer 61 that has its primary winding 62 connected across transmission line 45, a capacitor 63 in parallel with winding 58, and cathode 32. Screen grid 34 is connected to the anode-cathode circuit at terminal 64. The capacitor 63 is provided across the secondary winding 58 of each plate supply transformer 61 to prevent false operation of the receiver units, all of which are fed from a common plate supply, but such capacitor may not be required. Without capacitor 63, such false firing may occur when the anodes 31 of all tubes 28 are connected to a single transformer 61. The surge current caused by one tube 28 firing results in a momentary surge voltage applied to the anodes 31 of the other three tubes 28, causing them to fire if the bias is adjusted near the firing point. Capacitor 63 absorbs this surge and prevents false operation.

Relay 56 controls a signalling circuit which includes contacts 65, 66, a source of electrical energy, here shown as a secondary winding 67 of transformer 61, and a lamp 68a. The indicator lamp is designated 68a in receiver unit A, and the indicator lamps in receiver units B, C and D are designated 68b, 68c and 68d, respectively.

The mode of operation of the invention can best be understood by assigning values to the embodiment selected for illustration in Fig. 1. Tubes 28 are set to fire when the control grid 33 voltage is positive. The ouput of the oscillator-amplifier with no cars on track 11 is 3 volts at 100 cycles as measured across the rails 12, 13 at dotted line 18 and across the windings 25. The voltage from oscillator 21 across windings 25 when there is a car on track 11 at dotted line 18 is zero volts, at dotted line 17 is 0.5 volt, at dotted line 16 is 1.0 volt, at dotted line 15 is 1.5 volts and at dotted line'14 is 2.1 volts. Bias resistor 42a is set at 2.0 volts, 42b at 1.5 volts, 42c at 1.0 volt and 42d at 0.5 volt.

With no car on track 11, then, the voltage between cathode 32 and grid 33 of receiver unit A is 1.0 volt, of receiver unit B is 1.5 volts, of receiver unit C is 2.0 volts, and of receiver unit D is 2.5 volts. All the control grids 33 are positive, so all the tubes 28 are firing and all the lamps 68a-6Sd are extinguished.

Now, when a railroad car rolls into track 11 from the bottom end of the track 11 as shown in Fig. 1, its wheels first short circuit the rails 12, 13 at line 18 so that the voltage across windings 25 is zero, and the control grids have impressed thereon only the negative bias voltage. Under this condition all the tubes 28 cease firing, the relays 56 close across contacts 65, 66, and all the lamps 68a-68d are illuminated, lamp 68d of receiver unit D indicating the presence of a car in track section d. I

Then as the car passes line 17 and enters track section 0, the voltage across windings 25 becomes 0.5 volt and increases to overcome the 0.5 volt negative bias of resistor'42d, which causes tube 28 of unit D to fire and extinguishes lamp 68d to indicate that there is no car on track section d.

Similarly, as the car rolls down track 11 and passes section 0, lamp 68c is extinguished, and when it passes section b, lamp 68b is extinguished. The car stops in section a and lamp 68a remains illuminated. Succeeding cars fill up section a, and the first car to stop in section b causes lamp 68b to remain illuminated. This indicates to the tower operator that section a is filled and section b is starting to fill. Upon this signal, the operator applies more retarding force to the wheels of the succeeding cars to give them a slower speed into the classification track and cause them to stop in section b. As the track sections fill up, the lamps 68c and 68d will indicate that fact to the operator so that the speed of the cars can be properly adjusted.

It is important to note that the track sections can be shortened and increased in number, and receiver units provided for each section. With eight track sections, for example, finer control of the railroad car speed is obtained.

Turning now to the modification of this invention shown in Fig. 2, it will be noted that the circuitry is substantially the same as for any of the receiver units, and that like parts are designated by like numbers except that sufiix letters have been dropped, thus bias resistor 42, resistor 41 and lamp 68. The terminals of wires 23, 24 are connected across rails 71, 72 at any remote point and the passage of a train over that point is detected through the short circuit caused by the wheels which stops the tube 28 from firing and illuminates lamp 68. In this modification the frequency of the oscillator 21 is increased to shorten the length of the track control section. For example, with the frequency at 100 cycles per second, the length of the track control section is g, extending between dotted lines 73 and 74; while with the frequency at 400 cycles per second, the length of the track control section is 11, extending between dotted lines 75 and 76. Thus, higher frequencies pin-point the position of a train more accurately.

It is to be understood that the form of the invention herewith shown and described is to be taken as a preferred embodiment. Various changes may be made in the shape, size and arrangement of parts. For example, equivalent elements may be substituted for those illustrated and described herein, parts may be reversed, and certain features of the invention may be utilized independently of the use of other features, all without departing from the spirit or scope of the invention as defined in the subjoined claims.

Having thus described our invention, we claim:

1. Apparatus for detecting whether a predetermined track section of railroad yard track is occupied by a railroad car and for detecting the position of subsequent cars through a series of predetermined track sections of said railroad yard track, said apparatus comprising a railroad yard track having a pair of spaced parallel rails with each rail formed of a plurality of rail sections electrically connected together in end to end fashion, means for generating an electric voltage which decreases substantially with the increase of load thereon, means for impressing said voltage across said railroad yard track at a desired location, whereby the extent of voltage reduction varies according to the distance between a railroad car when occupying said track and said desired location at which said voltage is impressed on the track, and sensing means for detecting and signalling whether a predetermined track sec tion is occupied by a railroad car and for detecting the position of subsequent cars along a series of predetermined track sections of said yard track, said sensing means being connected across said railroad yard track and said means for generating an electric voltage.

2. The apparatus defined in claim 1, wherein said means for generating said electric voltage includes an oscillator, and an amplifier electrically connected to the output of said oscillator, and wherein said means for impressing said electric voltage across said railroad yard track at a desired location includes electrical conductors connecting the output of said amplifier to said desired location.

3. The apparatus defined in claim 1, wherein said means for generating said electric voltage is an oscillator.

4. The apparatus defined in claim 1, wherein said means for generating said electric voltage is an oscillator, and wherein is also provided means connected to said oscillator for varying the frequency of its output voltage.

5. The apparatus defined in claim 1, wherein said sensing means includes a plurality of transformers each having a primary winding and a secondary winding, electrical conductors connecting the output of said voltage generating means across each of said primary windings, a plurality of gas tubes having a control grid, a cathode, and an anode, each tube being connected to a separate transformer with one end of the secondary winding connected to its control grid and the other end of the same secondary winding connected to its cathode, a rectifier connected in series between the secondary winding and the control grid of each tube and adapted to pass a unidirectional current to said control grid, biasing means connected in series with the control grid of each tube so that each tube is biased differently so that the tubes stop firing at diifer- 6. The apparatus defined in claim 5, wherein said sensing means also includes an electromagnet relay having a,

tive, the tube is firing, and said relay operates to hold said bulb extinguished, and whereby when a railroad car is occupying said yard track the control grid is negative, the tube is extinguished, and the relay operates to illuminate the bulb.

7. Apparatus for detecting whether a railroad yard track is occupied by a railroad car and for detecting the position of subsequent cars on said railroad car track, said apparatus comprising a railroad yard track having a pair of spaced parallel rails, means for generating electric voltage which decreases substantially with the increase of load thereon, means for impressing said voltage across said railroad yard track at a desired location, whereby ent control grid voltages in response to different voltages the extent of voltage reduction varies according to the distance between a railroad car when occupying said track and said desired location at which said voltage is impressed on the track, and sensing means for detecting and signalling whether said railroad yard track is occupied bya railroad car and for detecting the position of subsequent cars from said desired location, said sensing means being connected across said railroad yard track and said means for generating an electric voltage.

References Cited in the file of this patent v UNITED STATES PATENTS Hawkins d June 11, 1907 898,324 Coe Sept. 8, 1908 1,324,912 Lewis Dec. 16, 1919 1,823,739 Horton Sept. 15, '1931 2,386,866 Jobin Oct. 16, 1945 2,655,594 Hanchett Oct. 13, 1953 2,724,745 Brewer Nov. 22, 1955 2,770,775 Agnew' Nov. 13, 1956 

